metlic53

iTrader: (1)

Ok I need a scale that tells me where you cannot hear it,,,,barely hear it,,,really hear it thump and it pounds the ground based on OVERLAp numbers.


My cam now has 7 degrees of overlap and runs great but it is mildly noticeable in exhaust note. I have a cam ordered with 14 degrees of overlap coming so I am sure it will be talking but the MS3 and MS4 talk pretty nastliy. Cam overlap guru please give me a CAM OVERLAP SCALE as it compares to exhaust note.
ALSO at what number does overlap influence gas mileage a little up to drinking it.
Thanks

Hamrdown

iTrader: (25)

If you want sound but a Thumper cam. All joking aside, I read a lot of people looking more for sound on here lately. You know, you can get big sound in a smaller cam with a tighter LSA & have the idle turned down. 7 degrees can sound pretty nasty with long tubes, no cats, the right mufflers, & a lower idle. My guess is either your exhaust system isn't right for your tune needs or the idle is too high.

JakeFusion

iTrader: (7)

7 degrees should thump. It's not thumping because your tune is off. You need to lean it out and play with the timing at idle. You can also lower your idle to get more thump.

Idle it at 750, lean it out to 16:1, and try timing in the 24-28 degree range. Watch your kPa readings and when you get the strongest (lowest number), you'll have a pretty solid idle. The chop really comes from the lean condition/stumble.

metlic53

iTrader: (1)

Im not looking for sound i was wondering if there is a "Rule of thumb" for how hard or not the LS based cams sound and their fuel economy.

JakeFusion

iTrader: (7)

Your original post talks mostly about sound.

Anything over 8 degrees is going to not drive like stock. Anything under 8 degrees will be streetable (i.e., little to no surging at low RPM and an idle that will be tame enough to sit in traffic with the A/C going that won't try to die when the clutch is depressed). 4 degrees is really the cutoff for no surging and truly "stock-like" manners. Of course, you can make a cam with 14 degrees of overlap behave... it just won't behave like stock.

As you approach 0 or less you get less of a fuel smell at idle and will be closer to passing emissions.

And the sound is totally dependent on the tune. A stock cam can thump. A cam with 16 degrees of overlap can purr. Neither will idle properly with those settings, but that's something to consider.

analyte

iTrader: (5)

Jake,
Won't that scale shift up or down depending on the size of the engine? 8 deg limit for 5.7, but maybe 9 deg for a 6.0?

Kip Fabre

It's not and exact. You need two thing. 1 what cubic inches? 2 how much static compression? Example 80's 350 CI small block chevy's had 8.5 compression there was a company making cams call (High ------) they were 218/218/106 that gives 6.0 degrees of overlap. They would hardly idle very little vacuum with no sound. The only sound was it sounded like it was going to die. NO power until 3500 then it was only equal to the stock cam. The reason there was no sound is because there was no compression. Now take the same engine and make it 11:1 and here comes the sound. Larger cubic inches will sound much better than a smaller cubic inch engine. So to have a good sound you need cubic inches and static compression. Long tube headers will help. Your tuner can also help. You also need some amount of overlap but that will very.

JakeFusion

iTrader: (7)

Yeah. It changes. The 5.7 is what I was referring to. But it's not a huge difference. You can absorb more overlap with a larger engine... say a 408 can take 12-16 degrees and still be pretty streetable. There are some that would say that it's not that big of a difference. It's all pretty personal, so eh.

There are some other things to take into consideration as well. The duration @ .050" only provides part of the picture. Extremely fast lobes, like solid roller, or LSK or XE-R, have smaller seat-to-seat durations than slower lobes with equivalent .050" specs. Therefore, they produce more vacuum at idle and are easier to drive because they actually have less overlap at .006" of lift.

And as Kip points out, compression makes a difference too. High compression motors crackle and sizzle and make cars easier to drive.

squalor

iTrader: (3)

Thank you for this post Jake.

josh4ku

iTrader: (10)

Where would the streettable overlap cut off be for a 5.3 wih 9.5:1 compression?

Kip Fabre

That depends on what you call streettable. 5.3 small cubic inches 9.5 is low compression. Stock stall? Stick shift? Sea level? Denver ? If mine I would be way into the -@.05 if you had 11.5 you could use a much larger cam. What people must realize is 0 overlap @ .05 is not 0 overlap. On most of our cams it has a real 55 degrees on running overlap😃

josh4ku

iTrader: (10)

Stick shift , 2,700ft, 75 mm turbo , current cam is 222/227 113+3, also have a 217/223 114+4 and honestly not sold on either of them.

JAYSS10

I have cam to ask about I got a motor with a comp M1359-07 cam for ls1 ,its in a stock lq4 anyone run this or can give me info or vid of it running it going in z28 3500 stall 3,73 gear na

Kip Fabre

The turbo will make the power so if mine and am I wanted streetable I would use a 205/218/116/+6

josh4ku

iTrader: (10)

I'll call you this afternoon

Rise of the Phoenix

iTrader: (27)

Depends on the person. What's streetable for me may not be streetable for you.

My cam has 11 degrees of overlap and it's completely streetable. Also depends a ton on the tune. A good tuner can make those bigger cams drive like a Cadillac, and a shitty tuner can make a small/baby dick cam drive like it's Ron Jeremy.

JakeFusion

iTrader: (7)

My cam has 16 degrees of overlap and a 3.23 rearend. So at like 45 mph locked up in OD, I'm around 1300 RPM. It drives absolutely fine there. Here's a video:

thunderstruck507

iTrader: (18)

I agree that the sound relies a lot on the tune. I have one of the Cam Motion 5.3 "drop in" cams in my 5.3 truck. Depending on the tune it can sound like stock or shake the whole truck. Once the truck gets longtubes I can probably make the exhaust note even more pronounced.